Commentary Inf XIX 46-47

The pope's situation is reminiscent of St. Peter's upside-down crucifixion (see Herzman and Stephany [Herz.1978.1, p. 44]), but also refers to the Florentine mode of dispatching convicted assassins, 'planting' them upside down in a hole and then suffocating them when the hole is filled back up with earth: 'Let the assassin be planted upside down, so that he may be put to death.' Perhaps the earliest commentator to make reference to this 'ancient decree' of Florence is Rossetti (DDP Rossetti.Inf.XIX.46-51).